ST1968 is a novel camptothecin derivative which interacts with topoisomerase I-DNA complex, inducing S-Phase specific cytotoxicity. It is endowed with a potent antitumor activity and an increased Therapeutic Index with respect to the clinically used analogues (i.e.irinotecan and topotecan) in some xenograft models (ovary, colon, head & neck, cervix). Anti-tumor activity has been also noted in platinum resistant ovarian cell xenografts and in topoisomerase I mutant prostate cell lines. The acceptable toxicity profile in animals and the activity in camptothecin-resistant cell lines make ST1968 a good candidate for clinical trials.